Manufacturing method for mold sets and resin molded products

Abstract

The primary objective of this technology is to improve the number of resin molding shots when the sealing layer is repeatedly used, while ensuring the sealing performance of the joint surfaces between the two or more molds in a mold set for molding resin in a cavity formed by joining two or more molds. [Solution] The mold set of this technology is a mold set for molding resin in a cavity formed by joining two or more molds, wherein a sealing layer containing urethane resin is provided on at least one of the joining surfaces of the two or more molds, grooves are formed on the surface of the joining surface, and the components of the sealing layer are filled into the grooves.

Description

Technical Field

[0001] This technology relates to a mold set and a method for manufacturing a resin molded product.

Background Art

[0002] Conventionally, a technique for molding resin using a mold has been known.

[0003] For example, Patent Document 1 below discloses a technique in which a urethane raw material is sprayed on a seal portion of a foam molding die to form a urethane foam that functions as a sealing material and also becomes a part of a molded product on the seal portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] This technology mainly aims to improve the number of resin molding shots when the seal layer provided on at least one of the joint surfaces of two or more molds is continuously used repeatedly while ensuring the sealing property of the joint surface in a mold set for molding resin in a cavity formed by fitting two or more molds together.

Means for Solving the Problems

[0006] This technology provides a mold set for molding resin in a cavity formed by fitting two or more molds together, wherein a seal layer containing a urethane resin is provided on at least one of the joint surfaces of the two or more molds, grooves are formed on the surface of the joint surface, and the components of the seal layer are filled in the grooves. Furthermore, this technology provides a method for manufacturing resin molded products by molding resin using the mold set of this technology. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of an example of a mold set provided with a sealing layer formed by the mold sealing material of this technology. [Figure 2] This is a cross-sectional view of an example of a mold set provided with a sealing layer formed by the mold sealing material of this technology. [Figure 3] This is a schematic diagram illustrating a resin molded product formed using the mold set of this technology. [Modes for carrying out the invention]

[0008] The following describes preferred embodiments for implementing this technology. The embodiments described below are examples of typical embodiments of this technology, and any combination of these embodiments is possible. Furthermore, this does not mean that the scope of this technology will be narrowed.

[0009] [Mold Set] In the manufacture of resin molded products, a mold set is used in which resin is molded within a cavity formed by joining two or more molds together.

[0010] This technology provides a mold set for molding resin in a cavity formed by joining two or more molds, wherein a sealing layer containing urethane resin is provided on at least one of the joining surfaces of the two or more molds, and furthermore, grooves are formed on the surface of the joining surface, and the components of the sealing layer are filled into the grooves. By having the above features, the mold set of this technology can improve the number of resin molding shots when the same sealing layer is repeatedly used while ensuring the sealing performance of the joining surfaces of the two or more molds. In addition, by providing the grooves at predetermined locations on the joining surface and filling the grooves with the components of the sealing layer, the generation of burrs (the generation of burrs exceeding the acceptable size) in the resulting resin molded product can be suppressed. This also leads to a reduction in the frequency of deburring processes.

[0011] Here, "fitting two or more molds" means, for example, that when the molds to be fitted together consist of a mold having a concave shape and a mold having a convex shape, the number of molds having concave shapes and molds having convex shapes may be the same or different. For example, the combination may consist of a mold having one concave shape and a mold having one convex shape, or it may consist of a combination where one mold having multiple concave shapes is paired with multiple molds having one convex shape. Alternatively, it may consist of multiple molds having one concave shape paired with multiple molds having convex shapes. In this specification, the terms "concave shape" and "convex shape" are used to clarify that the molds can be fitted together in a mold set, but these molds are not limited to the shapes of "concave shape" or "convex shape".

[0012] In the mold set of this technology, a groove is provided on at least one of the joining surfaces of the two or more molds, and a sealing layer containing urethane resin is provided by filling the groove. By providing the sealing layer containing urethane resin in this way by filling the groove formed on the joining surface, the sealing performance of the joining surfaces of the molds can be ensured, while improving the number of resin formation shots when the sealing layer (i.e., the same sealing layer) is used repeatedly.

[0013] In the mold set of this technology, the seal layer may be provided on both joining surfaces of the mating molds, or it may be provided on only one of the joining surfaces of two or more molds. For example, if the mating molds consist of a combination of a mold with a concave shape and a mold with a convex shape, the seal layer may be provided on the joining surface of the concave mold, or on the joining surface of the convex mold, or on both the joining surface of the concave mold and the joining surface of the convex mold. Depending on the molding conditions of the resin using the mold set and the physical properties of the resin to be molded, the seal layer can be formed at any position on the mold set using the mold seal material of this technology described later.

[0014] Here, the joint surfaces between molds on which the seal layer formed by the mold sealing material of this technology is provided are not limited to the outer edges of cavities formed by joining two or more molds together. For example, joint surfaces between molds are also formed in the portions of holes provided in the molds to form through portions in the resin molded product (these holes are usually located inside the cavity, etc.). Therefore, a seal layer formed by the mold sealing material of this technology can also be provided on such joint surfaces.

[0015] In the above mold set, the interlocking molds may be connected in a manner that allows them to be opened and closed through an opening and closing mechanism. When this configuration is adopted for the mold set, resin can be injected from any direction into the opening of the mold (open state) that constitutes the mounting surface, and after the resin has been injected, the other mold can be interlocked (closed state) by methods such as rotation, thus efficiently injecting resin into the cavity. It can be suitably used as a mold, especially when using foamed resin.

[0016] Here, the "opening and closing mechanism" is not particularly limited as long as it can operate to open and close the molds together. As an opening and closing mechanism, for example, a connecting member such as a hinge may be used to connect the molds so that they can rotate together. In this case, by rotating one mold relative to one mold that constitutes the mounting surface when the mold set is placed, the molds can be brought into contact with each other, forming a cavity for molding resin.

[0017] In the above mold set, the joining surfaces of the interlocking molds may be formed at an inclination with respect to the mounting surface on which the mold set is placed. For example, if the interlocking molds are connected so as to be openable and closable through an opening and closing mechanism, forming the joining surfaces at an inclination with respect to the mounting surface on which the mold set is placed, on a mold set that is rotatably mounted via a connecting member such as a hinge, allows for suitable interlocking of the molds when the molds are rotated and enables suitable opening and closing of the molds.

[0018] In other embodiments, the opening and closing of the molds may be performed not by an opening and closing mechanism using a connecting member such as a hinge, but by an opening and closing mechanism equipped with a reciprocating mechanism such as a sliding mechanism. In this case, the opening and closing operations of the molds (mold opening, mold closing) are performed by the sliding mechanism or the like.

[0019] The sealing layer provided in the mold set of this technology contains a urethane resin. Preferably, the urethane resin is not foamed (i.e., non-foamed), as long as it does not impair the purpose of this technology. That is, the urethane resin used in the mold sealing material is not so-called urethane foam. Furthermore, the urethane resin is not formed with the intention of becoming part of a molded product. In this technology, "not foamed" means that foaming has not been intentionally induced. For example, if a small portion of the resin naturally foams due to moisture in the air when forming the sealing layer using the mold sealing material of this technology, this is not intentional foaming and is therefore included in the concept of "not foamed."

[0020] Here, the "urethane resin" is a polymer compound having a urethane bond formed by the reaction of a polyol component and a polyisocyanate component. The urethane resin that can be used for the seal layer of the mold set of the present technology can be synthesized under any conditions by combining any polyol component and polyisocyanate component. Any urethane resin that can be synthesized in this way is not particularly limited, but among such urethane resins, a urethane resin having a polyester structure is particularly preferred. As the polyester structure, in particular, a polycaprolactone structure derived from a caprolactone structure and formed by ring-opening the caprolactone structure is preferred. More specifically, a urethane resin synthesized by combining a polyester polyol component and any polyisocyanate component under any conditions, more preferably, any polycaprolactone polyol component produced by ring-opening polymerization using a caprolactone monomer and any isocyanate component are combined and synthesized. By using it as the urethane resin related to the seal layer provided in the mold set of the present technology, while improving the durability of the seal layer, the sealing property of the joint surface between the molds can be more suitably ensured.

[0021] The seal layer provided in the mold set of the present technology can further effectively improve the durability by increasing its thickness. In the mold set of the present technology, a groove is formed at the position where the seal layer is provided on the surface of the joint surface between two or more molds, and the thickness of the seal layer can be adjusted by filling the groove with the components of the seal layer.

[0022] In particular, since the seal layer included in the mold set of the present technology contains a urethane resin, before forming the seal layer on the mold, a mixture and agitation of a first liquid containing a polyol and a second liquid containing a polyisocyanate (the raw material composition of the seal layer) is applied to the target position, and then cured to form it. That is, since the above raw material composition is applied in a low-viscosity state before the reaction for synthesizing the urethane resin ends, by providing a groove at the position on the surface of the joint surface between the molds where the seal layer is to be provided, the raw material composition applied suitably can be held, and the seal layer can be formed at the target position. When the raw material composition of the seal layer cures in the groove, the seal layer adheres closely to the surface in the groove due to its own adhesive force developed during the curing process. Also, as described above, since the seal layer included in the mold set of the present technology is not formed for the purpose of being a part of the molded product, even if a groove is provided on the joint surface of the mold, it does not affect the shape of the resin molded product manufactured using the mold set.

[0023] Also, in the mold set of the present technology, by forming the groove, the contact area between the seal layer and the mold per unit area of the joint surface of the mold can be increased, thereby improving the adhesion strength between the seal layer and the mold. As long as the object of the present technology is not impaired, a part of the seal layer may protrude from the groove and be formed on the surface of the joint surface.

[0024] In the mold set of the present technology, the shape of the groove formed on the joint surface between the molds is not particularly limited. For example, the cross-sectional shape of the groove can be an arbitrary shape such as an arc shape.

[0025] Furthermore, in the mold set of the present technology, the surface of the groove where the seal layer is provided may be subjected to a roughening treatment. By the roughening treatment, the surface area per unit area of the surface where the seal layer made of the mold sealing material joins the mold can be further increased, so that the joining strength between the two can be further improved. Thereby, the durability of the seal layer can be suitably maintained.

[0026] Surface roughening can be performed using any method, such as sandpaper or shot blasting. When roughening is done with sandpaper, the grit size of the sandpaper used should be, for example, #100 to #180. After the surface roughening treatment, it is preferable to avoid touching the roughened surface.

[0027] In the mold set of this technology, the depth and width of the grooves formed on the surface of the joining surfaces of two or more molds are not particularly limited, as long as they can hold the reaction liquid in which the urethane resin is synthesized, according to the characteristics of the reaction liquid. The depth of the grooves formed on the surface of the joining surfaces of two or more molds can be adjusted to, for example, 2 mm or more, 3 mm or more, 4 mm or more, etc. Furthermore, there is no particular upper limit to the depth of the grooves, but it can be adjusted to a range such as 5 mm or less. Here, the "depth of the groove" refers to the maximum value of the depth relative to the joining surface.

[0028] Similarly, the width of the groove formed on the surface of the joint between two or more molds is adjusted to, for example, 2 mm or more, 4 mm or more, 6 mm or more, etc. Furthermore, there is no particular upper limit to the width of the groove, but it can be adjusted to a range such as 60 mm or less, 40 mm or less, 20 mm or less, 10 mm or less, etc. Here, the "groove width" is defined as the minimum vertical distance from one side of the groove to the other side.

[0029] Furthermore, in the mold set of this technology, the grooves are filled with components of the sealing layer, but the width and thickness of the sealing layer do not necessarily match the width and depth of the grooves, and can be adjusted within a range larger than the above range.

[0030] Furthermore, when the sealing layer is provided within a groove formed on the joint surface, a portion of the sealing layer exposed from the groove opening (the exposed portion) will be raised outward from the groove opening so that it is at a higher height than the joint surface. The thickness (maximum value) of this outwardly raised portion (exposed portion) is not particularly limited as long as it does not impair the purpose of this technology, but for example, it may be in the range of 0.05 mm to 3 mm at a temperature of 23°C.

[0031] Figure 1 is a perspective view of an example of a mold set of this technology. The mold set 100 shown in the figure consists of two molds 101 and 102. In the mold set shown in Figure 1, mold 101, which forms the mounting surface when the mold set is placed on it, has a concave shape, and the other mold 102 has a convex shape. The concave mold 101 and the convex mold 102 are connected via a hinge 103 so as to be able to be opened and closed as an opening and closing mechanism. As a result, by rotating the convex mold 102 relative to the concave mold 101 which forms the mounting surface when the mold set is placed on it, the molds can be mated together to form a cavity 104 for molding resin.

[0032] Figure 2 is a cross-sectional view taken from the direction indicated by the arrow in Figure 1, in the XY plane (a cross-section perpendicular to the mounting surface 108 on which the mold set 100 is placed) in Figure 1, when the convex mold 102 is rotated to fit together the concave mold 101. By fitting together the concave mold 101 and the convex mold 102, a cavity 104 for molding resin is formed. A seal layer 106 is provided on the joint surface 105 between the molds at this time. In addition, grooves 107 are formed on the surface of the joint surface 105, and the components of the seal layer are filled into the grooves 107.

[0033] Furthermore, a release agent may be applied to the surface of the seal layer 106 to form a release layer. Here, the release agent is an agent used to efficiently remove the resin molded product from the mold set 100. By applying such a release layer to the surface of the seal layer 106, adhesion between the seal layer 106 and the resin molded product is suppressed, and the resin molded product can be efficiently removed from the mold set 100. As the release agent, a known release agent used during the molding of resin molded products can be used. For example, if the resin molded product is made of urethane resin foam, a known release agent used during the molding of the urethane resin foam (for example, product name "M975", product name "T-626", both manufactured by Chukyo Oil & Fat Co., Ltd.) can be used. Figure 3 is a schematic explanatory diagram showing a resin molded product 200 molded using the mold set 100 of this technology. The resin molded product 100 is formed in a cavity 104 that is created between the inner surface (mold surface) of the concave mold 101 and the inner surface (mold surface) of the convex mold 102.

[0034] In the examples shown in Figures 1 and 2, the seal layer 106 and groove 107 are provided on a concave mold 101. However, as mentioned above, depending on the molding conditions of the resin using the mold set and the physical properties of the resin to be molded, the seal layer and groove may be provided on the joint surface of a convex mold, or the seal layer and groove may be provided on both the joint surface of the concave mold and the joint surface of the convex mold. Furthermore, in the example shown in Figure 2, the cross-sectional shape of the groove 107 is arc-shaped, but the cross-sectional shape of the groove is not limited to this shape. In addition, although not explicitly shown in Figure 2, as mentioned above, the surface of the joint surface of the mold on which the seal layer is provided (including the surface of the groove) may be roughened.

[0035] [Physical properties of the sealing layer] The sealing layer of the mold set of this technology can have its durability improved by adjusting physical properties such as elongation, tensile strength, static friction, kinetic friction, or static compression.

[0036] For example, the elongation rate (at 60°C) of the sealing layer of the mold set of this technology may be adjusted to 40% or more. The elongation rate (at 60°C) of the sealing layer of the mold set of this technology is preferably 40% or more, more preferably 60% or more, and particularly preferably 80% or more.

[0037] Furthermore, while there is no particular upper limit to the elongation rate (at 60°C) of the sealing layer provided by the mold set of this technology, it can be adjusted to ranges such as 130% or less, 110% or less, or 100% or less.

[0038] The "elongation rate" mentioned above is measured in accordance with JIS K 6400-5. That is, in this specification, "elongation rate (60°C)" refers to the elongation rate measured in accordance with JIS K 6400-5 under 60°C conditions. Also, "elongation rate (23°C)" refers to the elongation rate measured in accordance with JIS K 6400-5 under 23°C (room temperature) conditions.

[0039] The elongation rate (at 23°C) of the sealing layer of the mold set of this technology is preferably 15% or less, more preferably 13% or less, and even more preferably 10% or less. Furthermore, there is no particular lower limit to the elongation rate (at 23°C) of the sealing layer of the mold set.

[0040] The elongation rate (60°C) of the sealing layer of the mold set is preferably greater than the elongation rate (23°C). In this case, the difference between the elongation rate (60°C) and the elongation rate (23°C) is preferably 40 percentage points or more, more preferably 45 percentage points or more, and even more preferably 50 percentage points or more.

[0041] Furthermore, if the elongation rate (60°C) of the seal layer of the mold set of this technology is greater than the elongation rate (23°C), it is preferable that the elongation rate (60°C) is 10% or more. When the seal layer of the mold set of this technology is heated (for example, when heated from 23°C to 60°C), the elongation rate in the longitudinal direction increases. In this case, the elongation rate (60°C) may be 20% or more, 40% or more, 60% or more, or 80% or more. Also, in this case, there is no particular upper limit to the elongation rate (60°C), but it can be adjusted to a range such as 130% or less, 110% or less, or 100% or less.

[0042] Furthermore, the tensile strength (23°C) of the sealing layer of the mold set of this technology may be adjusted to 20 MPa or higher. The tensile strength (23°C) of the sealing layer of the mold set of this technology is preferably 20 MPa or higher, more preferably 30 MPa or higher, and particularly preferably 40 MPa or higher. There is no particular upper limit to the tensile strength (23°C) of the sealing layer of the mold set of this technology, but it can be adjusted to ranges such as 100 MPa or less, 90 MPa or less, or 80 MPa or less.

[0043] The "tensile strength" mentioned above is measured in accordance with JIS K 6400-5. That is, in this specification, "tensile strength (23°C)" refers to the tensile strength measured in accordance with JIS K 6400-5 under room temperature conditions of 23°C. Also, "tensile strength (60°C)" refers to the tensile strength measured in accordance with JIS K 6400-5 under 60°C conditions.

[0044] The tensile strength (at 60°C) of the sealing layer in the mold set of this technology is preferably 1 MPa or higher, more preferably 3 MPa or higher, even more preferably 6 MPa or higher, and particularly preferably 8 MPa or higher. Furthermore, there is no particular upper limit to the tensile strength (at 60°C) of the sealing layer in the mold set of this technology, but it can be adjusted to ranges such as 20 MPa or less, 15 MPa or less, or 10 MPa or less.

[0045] The static friction force of the sealing layer in the mold set of this technology may be adjusted to 5N or less. Preferably, the static friction force of the sealing layer in the mold set of this technology is 3N or less, and particularly preferably 1N or less. Furthermore, there is no particular lower limit to the static friction force of the sealing layer in the mold set of this technology.

[0046] The dynamic friction force of the sealing layer in the mold set of this technology may be adjusted to 5N or less. Preferably, the dynamic friction force of the sealing layer in the mold set of this technology is 2N or less, and particularly preferably 1N or less. Furthermore, there is no particular lower limit to the dynamic friction force of the sealing layer in the mold set of this technology.

[0047] The "static friction" and "kinetic friction" mentioned above are measured in accordance with JIS K 7125. That is, in this specification, "static friction (23°C)" refers to the static friction measured in accordance with JIS K 7125 at a normal temperature of 23°C, and "kinetic friction (23°C)" refers to the kinetic friction measured in accordance with JIS K 7125 at a normal temperature of 23°C.

[0048] The static compression strain (60°C) of the seal layer in the mold set of this technology may be adjusted to 15 MPa or less. The static compression value (60°C) of the seal layer in the mold set of this technology is preferably 15 MPa or less, and particularly preferably 13 MPa or less. Furthermore, there is no particular lower limit to the static compression strain (60°C) of the seal layer in the mold set of this technology.

[0049] The "static compression strain" mentioned above is measured in accordance with JIS K 6400-2. That is, in this specification, "static compression strain (60°C)" refers to the static compression strain measured in accordance with JIS K 6400-2 under 60°C conditions. Also, "static compression strain (23°C)" refers to the static compression strain measured in accordance with JIS K 6400-2 under 23°C (room temperature) conditions.

[0050] Furthermore, the Asker D hardness (23°C) of the sealing layer of the mold set of this technology is preferably 40 or higher, more preferably 50 or higher, even more preferably 60 or higher, and particularly preferably 70 or higher. While there is no particular upper limit to the Asker D hardness (23°C) as long as it does not impair the purpose of this technology, for example, it is preferably 90 or lower, and more preferably 85 or lower.

[0051] [Method for forming a sealing layer] Next, a specific method for providing a sealing layer on the joining surfaces of the molds in the mold set of this technology will be described. Note that these are just examples of preferred methods for forming a sealing layer on the joining surfaces of the molds in the mold set, and any necessary steps can be omitted or added as needed.

[0052] <Mold cleaning> First, it is preferable to clean the molds that constitute the mold set for which the sealing layer is provided. The molds can be suitably cleaned using any solvent or dry ice appropriate to the resin being molded, under known cleaning conditions.

[0053] <Mold release agent application> Next, a release agent is applied (as an example) to the surface of each mold constituting the cavity using a brush or the like. A known release agent, such as a urethane release agent, can be suitably used as the release agent.

[0054] <Leg attachment> Next, the surface of the joint surface of the mold to which the seal layer is provided (including the surface of the groove) may be roughened. Roughening increases the surface area of ​​the joint between the mold seal material and the mold, which can improve the joint strength between the two. The roughening treatment can be carried out using any method, such as sandpaper. When roughening is performed with sandpaper, the grit size of the sandpaper used should be, for example, #100 to #180. After roughening, it is preferable to avoid touching the roughened surface.

[0055] <Sealant application> Next, a first liquid (liquid A) containing a polyol component and a second liquid (liquid B) containing a polyisocyanate component are mixed and stirred to produce a raw material composition containing urethane resin raw materials. The stirring time at this stage is not particularly limited, as long as the conditions allow for sufficient stirring of liquids A and B. For example, any time can be adjusted as the stirring time, such as 5 to 20 minutes. The obtained raw material composition is applied to predetermined locations on the joint surfaces of the molds. Known coating methods such as brushes, sprays, and syringes can be used to apply the raw material composition.

[0056] <1st curing> The raw material composition applied to a predetermined location on the bonding surface undergoes a curing period, during which the urethane resin synthesis reaction proceeds and hardening is completed. While there are no particular restrictions on the curing time, it is typically around 1 to 3 hours.

[0057] <Finishing> After curing, it is preferable to smooth the shape of the formed seal layer by finishing the burrs. The method of finishing the burrs is not particularly limited, and any method can be used. For example, the shape of the seal layer can be smoothed by removing excess burrs from the seal layer using any cutting tool such as a chisel or cutter.

[0058] <Second curing> After deburring, it is preferable to allow the mold to cure for a certain period of time. The curing time is not particularly limited, but for example, it is about the same amount of time as the initial curing (for example, about 1 to 3 hours).

[0059] <Mold fitting confirmation> It is preferable to confirm whether the seal layer formed as described above is formed in a suitable position on the joining surfaces of the molds. This confirmation can be performed by any method, but for example, by applying red lead to the seal layer formed on the joining surfaces of the molds and then joining the molds together, it is possible to confirm whether the seal layer is formed in the desired position.

[0060] <Cleaning> Finally, any excess release agent or red lead adhering to the seal layer is removed. The method of removal is not particularly limited, and any method can be used. For example, these can be suitably removed with a solvent appropriate to the release agent.

[0061] Furthermore, when the resin molded product formed by the mold set is made of polyurethane foam, etc., it is preferable to apply a release agent to the surface of the seal layer in order to suppress the adhesion of a part of the foam to the seal layer. As the release agent, the known release agents described above may be used.

[0062] Furthermore, the sealing layer may be provided with grooves or slits, if necessary, to allow gas from inside the cavity to escape to the outside of the mold.

[0063] In the mold set of this technology, the seal layer formed in the groove can be removed from the groove and a new seal layer formed in the groove as needed. For example, if the seal layer exceeds a certain number of shots or if a predetermined period of time has elapsed, the seal layer in the groove can be replaced with a new seal layer as appropriate.

[0064] The sealing layer may be formed in an annular shape, encircling the cavity within the mold, or it may be formed with a portion of the annular shape missing. In other words, the sealing layer may be positioned to surround the resin molded product within the cavity, or it may be positioned only on a portion of the resin molded product.

[0065] [Manufacturing of resin molded products] In a mold set in which a sealing layer is provided by filling grooves formed on the joint surface using the above method, the sealing performance of the joint surfaces between molds can be ensured, while the number of resin molding shots can be increased when the sealing layer is repeatedly used.

[0066] The resins that can be molded using the molds of this technology are not particularly limited, and any resin can be suitably molded to produce resin molded products. For example, if the mold set of this technology is configured such that the interlocking molds are connected to each other in an openable and closable manner through an opening and closing mechanism, the ease of injecting resin into the cavity within the mold makes it particularly suitable for molding foamed resins. Examples of foamed resin molded products in this case include urethane foam molded using urethane resin, thermoplastic resin foam formed using thermoplastic resin, and thermosetting resin foam molded using thermosetting resin. In other embodiments, the mold set of this technology can also be used for molding non-foamed resins.

[0067] When molding foamed resin using the mold set of this technology, a gas passage may be provided to allow gas generated by foaming to escape from the cavity formed by joining the molds to the outside of the mold. The passage in this case is not particularly limited, but for example, it may be provided as a groove in the seal layer provided on the joint surface between the molds that leads from the inside of the cavity to the outside of the mold. When providing such a groove for a gas passage in the mold set of this technology, it may be provided in the seal layer so as to cross from the inside of the cavity to the outside of the mold. In this case, it is preferable that the groove is not to completely cut through the seal layer in the thickness direction, but rather to partially cut out the seal layer in the thickness direction in an arbitrary shape such as a concave shape. Alternatively, the above groove may be provided at multiple locations in the seal layer.

[0068] Furthermore, in the mold set of this technology, by providing a sealing layer at a predetermined location on the joint surface (a location where the distance between the cavity and the sealing layer is within a predetermined range), the amount of burrs formed around the resin molded product can be kept to a minimum.

[0069] The method for molding resin molded products using a mold set is not particularly limited as long as it does not impair the purpose of this technology. For example, injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding methods such as gas-assisted molding, molding using a heat-insulating mold, molding using a rapidly heated mold, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating) molding, etc.

[0070] Furthermore, the materials constituting each mold in the mold set are not particularly limited, as long as they do not impair the purpose of this technology. For example, they may be made of metallic materials consisting of metal or alloy, or they may be made of known mold materials other than the aforementioned metallic materials (e.g., resin materials).

[0071] Furthermore, this technology can also be configured as follows. [1] A mold set for molding resin in a cavity formed by joining two or more molds, A sealing layer containing urethane resin is provided on at least one of the joining surfaces of the two or more molds. A mold set in which grooves are formed on the surface of the joining surface, and the components of the sealing layer are filled into the grooves. [2] The mold set according to [1], wherein the surface of the groove is subjected to a roughening treatment. [3] The mold set according to [1] or [2], wherein the joining surface is formed at an inclination with respect to the mounting surface on which the mold set is placed. [4] The mold set according to any one of [1] to [3], wherein the elongation rate (60°C) of the sealing layer is 40% or more. [5] The mold set according to any one of [1] to [4], wherein the elongation rate (60°C) of the sealing layer is greater than the elongation rate (23°C), and the elongation rate (60°C) is 10% or more. [6] The mold set according to any one of [1] to [5], wherein the tensile strength (23°C) of the sealing layer is 20 MPa or more. [7] The mold set according to any one of [1] to [6], wherein the static friction force (23°C) of the sealing layer is 5N or less. [8] The mold set according to any one of [1] to [7], wherein the kinetic friction force (23°C) of the sealing layer is 5N or less. [9] The mold set according to any one of [1] to [8], wherein the static compression strain (60°C) of the seal layer is 15% or less.

[10] The mold set according to any one of [1] to [9], wherein the urethane resin has a polycaprolactone structure.

[11] The mold set according to any one of [1] to

[10] , wherein the two or more molds are connected to each other so as to be openable and closable through an opening and closing mechanism. A method for manufacturing a resin molded product, which involves molding resin using a mold set described in any of [1] to

[11] .

[13] The method for manufacturing a resin molded article according to

[12] , wherein the resin is a foamed resin.

[14] The method for manufacturing a resin molded article according to

[12] or

[13] , wherein the foamed resin is a urethane resin. [Examples]

[0072] The present technology will be described in more detail below using examples. However, the present technology is not limited in any way to the examples shown below.

[0073] [Raw materials] ◆First solution (Solution A) containing polyol components Polyester polyol (polycaprolactone polyol) / (A-1) / Appearance (room temperature): Liquid, Viscosity: 10 mPa·s, Acid value: 0.50 KOH mg / g, Hydroxyl value: 305.6 KOH mg / g, Number of functional groups: 3, Number average molecular weight: 550 • Polycarbonate polyol / (A-2) / Number average molecular weight 1000 • Polyether polyol (polypropylene oxide with ethylene oxide at the end) / (A-3) / Hydroxyl value 35 mg KOH / g, number of functional groups 3, number average molecular weight 5000 • Polyfunctional polyether polyol / (A-4) / Hydroxyl value 445, viscosity 8,000 (mPa·s at 25℃) ◆Second solution (Solution B) containing polyisocyanate components • Polyisocyanate: Polymeric MDI (Crude MDI) / (B-1) / NCO%:34% • Polyisocyanate: Polymeric MDI (Crude MDI) / (B-2) / NCO%; 31.3%

[0074] [Formation of the sealing layer] Using a mold set equipped with a configuration that allows the molds to be rotatably connected to each other using connecting members such as hinges, a sealing layer was formed on the joint surfaces of the molds in the mold set according to the procedure shown below. The internal surface area of ​​the cavities of the mold sets used in the examples and comparative examples was 500 cm². 3 In this cavity, the circumference of the joint surface where the seal layer is provided is 15 cm. Furthermore, the cross-sectional shape of the groove formed on the joint surface between the molds is an arc shape, as in Figure 2, and the maximum relative depth to the joint surface (groove depth) was designed to be 2 mm, while the minimum vertical distance from one side of the groove to the other (groove width) was designed to be 6 mm.

[0075] A mold release agent (product name M-975, manufactured by Chukyo Yushi Co., Ltd.) was applied to the joint surface of the mold to be fitted with the sealing layer of the mold set, which had been cleaned using a solvent (solvent name NMP, manufactured by Sanwa Yuka Kogyo Co., Ltd.) or dry ice. Subsequently, the surface of the joint surface of the mold to be fitted with the sealing layer was roughened using sandpaper (#60).

[0076] A raw material composition was prepared by mixing 28 g of a first liquid (Solution A) containing a polyol component and 21 g of a second liquid (Solution B) containing a polyisocyanate component in the combinations shown in Table 1, and stirring for 10 minutes. The obtained raw material composition was applied to the joint surfaces of the molds of the mold set under room temperature conditions of 25°C, so that the raw material composition filled the grooves. The application time was 5 minutes. It was confirmed that the mold set could suitably retain the low viscosity raw material composition before the reaction in which the urethane resin was synthesized was completed by forming grooves on the joint surfaces of the molds. The seal layer formed in this way had a thickness of 2 mm and a width of 6 mm. Application was carried out using a spatula or syringe.

[0077] After curing the mold with the sealing layer for 2 hours following the coating, excess burrs were removed from the sealing layer using a cutter, and the shape of the sealing layer was refined. After the burr removal, the mold was cured for another 2 hours.

[0078] Afterward, the molds were joined together with a seal layer formed on the joint surface between the molds to confirm that the seal layer was formed in the desired position. Then, any excess release agent or the red lead adhering to the seal layer was removed.

[0079] [Evaluation of physical properties of the sealing layer] The physical properties of the sealing layers provided in each mold set obtained above were measured in accordance with the following standards. The measurement results are shown in Table 1. • Elongation rate (23°C) and elongation rate (60°C): JIS K 6400-5 • Tensile strength (23°C) and tensile strength (60°C): JIS K 6400-5 • Static friction force (23°C) and kinetic friction force (23°C): JIS K 7125 • Static compression strain (23°C) and static compression strain (60°C): JIS K 6400-2

[0080] [Table 1]

[0081] [Mold durability evaluation] Using the mold sets obtained above, molded products of polyurethane resin, a foaming resin, were manufactured under the following conditions. Molding was repeated until defects such as rupture occurred in the seal layer. The number of moldings until defects such as rupture occurred in the seal layer was measured as the number of shots. As a reference example, the number of shots was also measured under the same conditions for a mold set using aluminum powder-containing epoxy resin (product name KAN Putty, manufactured by Kansai Putty Chemical Co., Ltd.) as the seal layer. The results are shown in Table 2.

[0082] <Molding conditions> • Pressure during molding: 3 MPa

[0083] <Resin raw materials used in molding> ◆First liquid containing polyether polyol as the polyol component ◆Second solution containing monomeric MDI as a polyisocyanate component ◆Foaming agent ·water ◆Blending ratio (mass ratio) Polyether polyol:polymer MDI = 65:35

[0084] [Table 2]

[0085] The results obtained confirm that the sealing layer provided on the joint surface between molds contains urethane resin, and by adjusting the elongation rate (60°C) to a certain range or higher, the number of shots in resin molding can be improved. Furthermore, it can be confirmed that the number of shots in resin molding can also be improved by adjusting the tensile strength (23°C) to a certain range or higher.

[0086] In Examples 1 and 2, no defects such as rupture of the seal layer occurred even when the number of molding cycles (shots) exceeded 5000. However, in Examples 1 and 2, although no defects such as rupture of the seal layer were observed, the experiment was terminated after exceeding 5000 cycles.

[0087] In Comparative Example 1, the seal layer tore during the first molding. In Comparative Example 2, the seal layer tore during the seventh molding. In Comparative Example 3, the seal layer ripped during the 200th molding.

[0088] In the example shown, the seal layer ruptured during the 600th molding cycle.

[0089] Furthermore, the Asker D hardness (23°C) of each seal layer in Examples 1 and 2 and Comparative Examples 1 to 3 was as follows: 73 (Example 1), 79 (Example 2), 76 (Comparative Example 1), 22 (Comparative Example 2), 23 (Comparative Example 3). [Explanation of Symbols]

[0090] 100 mold set 101 Concave mold 102 Convex mold 103 Opening / Closing Mechanism (Hinge) 104 Cavity 105 Joint surface 106 sealing layer 107 Groove 108 Mounting surface 200 Resin molded products

Claims

1. A mold set for molding resin in a cavity formed by joining two or more molds together, A sealing layer containing urethane resin is provided on at least one of the joining surfaces of the two or more molds. A mold set in which grooves are formed on the surface of the joining surface, and the components of the sealing layer are filled into the grooves.

2. A method for manufacturing a resin molded product by molding resin using the mold set described in claim 1.

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